EARLY DEVELOPMENT OF GRAFFILLA. l8l 



n-\cal any binucleated ova, except of course at the extreme tip, 

 nor has the slightest evidence been secured of nuclear divisions 

 either mitotic or amitotic throughout the entire length of a fully 

 matured ovary. We are therefore forced to the conclusion that 

 what \\r have described in connection with the absorption of 

 yolk furnishes the key to the twin condition in Gnifilla. It can 

 ii"i IK- argued that the breaking down of the membranes is only 

 apparent and therefore an artifact produced by reagent-. I'or 

 it ha- been observed in preparations made from material pn - 

 -er\e<| in a dozen different fixing fluids, and t".ll..\\ed by as many 

 di Herein -tain-. However, not in all ca-e- do the two contiguous 

 ova l"-e their intervening membranes, but some become com- 

 pletek -iirroimc|ed by vitelline cells, which through a process 

 <!' di-inii ^ration form the yolk mass of the definitive capsule 

 3. 7, 16). In such cases the two ova d> not lo-r iheir "in- 

 di\ idnalii\ ." and a subsequent reorganization of ne\\ meinbrane- 

 alioin ihe i\\o nuclei will not lake place. Considerable evidence 

 ha- been se< nred which indicates that the-e tuo method- of 

 cap-ule formation are but the extremes of one and the -aim- 



pi 01 ess. 



Throughout the entire history of yolk ab-orption main inter- 

 e-iing (han^es, involving both the nuclei:- and c\ topla-m, are 

 seen, but \\e can not deal with all of them In r < >ur attention 

 mu-t then-lore be directed to those that stem- to u- to be mo-t 

 impi ii i ant . 



In I'ig. 14 is represented a pair of nuclei lying within a single, 

 niembraiu The lower of these is immediately -urroumled 1\ a 

 la\er ot tinelv granular protoplasm, about which one can trace 

 another \et\- delicate, but neverthele distinct, membrane. 

 Thi- condition has been observed in a number of ova, and may 

 begin before the binucleated stage- is reached, that i-, in ova 

 -ituaud from two to six cells from the tip of the ovary. I have 

 not been able to demonstrate the universality of thi- membrane, 

 and I am therefore inclined to regard it a- the intra-cellular or 

 intra-\ itelline membrane that i- sometimes laid down about 

 the ovarian nucleus. It may be that in Graffilla it marks the 

 beginning of the segregation of the protoplasm from the yolk, 

 and is then-fore the first step in the reorganization of a cell about 

 each of the nuclei in the capsule. 



